The present invention relates to an electro-optical device and an electronic apparatus which use an electro-optical material such as liquid crystal and an electroluminescent (EL) material.
As is generally known, electro-optical devices are widely used as display units for electronic apparatuses. Typical examples of such display units are liquid crystal displays and electroluminescent (EL) displays. Such an electro-optical device generally comprises a substrate for carrying an electro-optical material, such as liquid crystal and an electroluminescent element, and electrodes for applying a voltage to the electro-optical material. For this type of electro-optical device, a structure has been suggested in which wiring for supplying signals to the electrodes is provided and extended toward the edges of the substrate while being connected to an IC chip which is mounted on the substrate by the chip-on-glass (COG) method.
The above-described structure, however, has a problem in that the wiring extending toward the edges of the substrate are exposed to outside air and thus the exposed portions easily suffer from corrosion caused by deposition of water or the like. From the viewpoint of wiring resistance and the like, the wiring are preferably composed of a metal such as aluminum; however, since such a metal is vulnerable to corrosion, the above problem is more noticeable.
The present invention has been made in view of the above circumstances and aims to provide an electro-optical device and an electronic apparatus which suffer less from corrosion of the wiring formed on the substrate.
To overcome this problem, an electro-optical device of the present invention comprises: a substrate carrying an electro-optical material; a first wiring formed on the surface of the substrate; an insulating layer for covering the first wiring, the insulating layer being formed on the surface of the substrate; and a second wiring formed over a first region of the insulating layer including a region overlapping a region in which the electro-optical material is formed and a second region which corresponds to the remaining region other than the first region of the insulating layer, the second wiring being connected to the first wiring via a contact hole formed within the first region of the insulating layer.
With this structure, since the first wiring is covered with the insulating layer, corrosion of the first wiring due to deposition of moisture or the like can be prevented. Moreover, since a contact hole for connecting the first wiring to the second wiring is formed in the first region including the region overlapping the region in which the electro-optical material is formed, moisture can be prevented from reaching the vicinity of the contact hole. Accordingly, when, for example, the second wiring is made of a material which readily permeates moisture, the moisture does not permeate through the second wiring and reach the first wiring. Thus, corrosion of the first wiring can be reliably prevented.
When the above electro-optical device is applied to a liquid crystal display using liquid crystal as the electro-optical material, the electro-optical device includes a counter substrate for holding the electro-optical material between the substrate and the counter substrate and a sealing material disposed between the substrate and the counter substrate. In such a case, the first region preferably includes a region of the insulating layer facing the sealing material. That is, when the contact hole is formed in the region of the insulating layer overlaid with the sealing material, moisture can be prevented from reaching the vicinity of the contact holes, and corrosion of the first wiring can be reliably suppressed.
Furthermore, in order to overcome the above problem, an electro-optical device of the present invention comprises: a substrate carrying an electro-optical material; a first wiring formed on the surface of the substrate; an insulating layer for covering the first wiring, the insulating layer being formed on the surface of the substrate and having a mounting region overlaid with an electronic component mounted on the surface of the insulating layer; and a second wiring connected to the electronic component, the second wiring being formed on the surface of the insulating layer and connected to the first wiring via a contact hole formed within the mounting region.
According to this electro-optical device, as in the above, the first wiring is covered with the insulating layer to prevent corrosion of the first wiring. In addition, since contact holes for connecting the first wiring to the second wiring are provided in the region for mounting the electronic component, moisture can be prevented from reaching the vicinity of the contact hole. Accordingly, when, for example, the second wiring is made of material which readily permeates moisture, the moisture can be reliably prevented from reaching the first wiring, thereby securely preventing corrosion of the first wiring. An example of the electro-optical device is an integrated circuit having an output terminal connected to the second wiring. An example of the electronic component is a flexible substrate comprising a base having flexibility and a wiring formed on the surface of the base, the wiring being connected to the second wiring.
In the electro-optical device of the present invention, the first wiring is preferably made of an elemental metal or an alloy whereas the second wiring is preferably made of a conductive oxide. In this manner, the second wiring has a higher corrosion resistance than the first wiring; hence, the problem of wiring corrosion can be overcome even when a structure including a second wiring exposed outside is employed.
In an electro-optical device further comprising a pixel electrode for applying a voltage to the electro-optical material, the second wiring and the pixel electrode are preferably formed of the same layer. In this manner, the pixel electrode and the second wiring can be made in the same step, thereby reducing the manufacturing cost. Note that in this case, both the pixel electrode and the second wiring may be made of indium tin oxide (ITO).
To overcome the above problem, an electronic apparatus of the present invention comprises the electro-optical device described above. As is described above, in the electro-optical device of the present invention, corrosion of the wiring formed on the substrate can be prevented. Thus, the electronic apparatus using this electro-optical device is free from degradation of the display quality caused by the corrosion of the wiring of the electro-optical device.